It has been required in various fields to make the surface of a hydrophobic material hydrophilic. For example, it is required to make the surface of plastics, fibers, ceramics and like materials hydrophilic. Taking synthetic fibers, for example, if the surface of polyester, polyolefin and like synthetic fibers can be made hydrophilic, their use for clothing such as underwear and their industrial use such as wipers are expected to be further increased. It is important in industries to provide a technique of forming richly versatile molecules as a method of manufacturing a chemically adsorbed film, which is hydrophilic to a desired extent.
Heretofore, plasma treatment or the like is well known as means for making the surface of plastics, fibers, ceramics and like material hydrophilic.
As a different means, the Ogawa method has been proposed in which functional groups having particular functions are incorporated in advance in a surface active material for chemical adsorption to form a specific chemically adsorbed film, as disclosed in, for example, U.S. Pat. No. 4,673,474.
However, plasma treatment can not impart a sufficient hydrophilic property. In addition, its process is complicated. Further, with the above Ogawa method it is difficult to incorporate in advance hydrophilic groups in the surface active material itself, thus imposing great restrictions on the manufacture of chemically adsorbed films which are hydrophilic to a desired extent. That is, this method is poorly versatile.
When the relative humidity is high or during the low temperature winter season, fog may be produced, for example, on vehicle window glass or on bathroom mirrors. Fog is produced due to inferior heat conductivity of the optical substrate of the vehicle window glass or bathroom mirror. When the atmospheric temperature is suddenly increased or when one surface contacts a high temperature air atmosphere while the other surface remains cool, water content in the air is condensed on the surface. This is referred to as fog. In the rainy season, for example, the relative humidity of air is saturated, and fog is readily produced with condensation as one breathes or sweats. It is well known in the art to prevent this fog formation by applying coating chemicals or resins containing hydrophilic compounds such as polyvinyl alcohol and polyethylene glycol on the optical material surface or applying hydrophilic film thereto.
However, by coating hydrophilic resins on the optical material surface or applying hydrophilic film thereto, the transparency of the material is sacrificed. In addition, separation or flaws may occur. Further, the method of coating hydrophilic chemicals or resins poses problems in that durability is low, although the cost is low.
Heretofore, there have been various proposals of providing a fog-proof property to the surface, which can be readily fogged by steam or water drops such as on window glass, bathroom mirrors and glass lenses.
There are many proposed methods of improving the fog-proof property of glass, plastic and other substrates; for example a method of coating a hydrophilic coating film of denatured polyethylene glycol or poly(hydroxyethyl methacrylate) or a method of coating various silicone-based resins.
The silicone-based resins, however, are less transparent, and therefore they require a very small coating thickness if they are to be coated while maintaining the color tone or luster of the substrate. However, since they are less hard and have an inferior scratch-proof property, by reducing the thickness of coating film durability is reduced. Likewise, denatured polyethylene glycol or poly(hydroxyethyl methacrylate) is poorly wear-resistant and inferior in durability.